Many existing chairs have vertical height adjustment mechanisms that include vertically extendable gas springs. Typically, the gas spring includes an actuator that extends above the gas spring into an area under a chair seat, and the seat includes a lever that can be manipulated by a seated user to unlock the gas spring. Upon release, the gas spring biases the seat upwardly. Alternatively, the seated user can, after unlocking the release button, press downwardly on the chair (such as by applying their bodyweight) to overcome the bias of the gas spring to force the seat downwardly. Once the desired vertical positioning has been achieved, the user can cease actuation of the lever, thus locking the gas spring (and the seat) at the desired height.
Vertically adjustable chairs are limited as they generally remain at the last height to which the chair was purposefully adjusted. For example, if the chair was last adjusted by a user that was shorter than average, the chair would remain at a height that is lower than a height comfortable for the average user. Likewise, if the chair was last adjusted by a user that was taller than average, the chair would remain at a height that is higher than a height comfortable for the average user. Such an effect is most readily observed in a conference room having a plurality of vertically adjustable chairs where the chairs are noticeably positioned at a plurality of heights. Such a plurality of heights is generally undesirable for a number of reasons. For example, this non-uniformity of heights can be aesthetically unappealing to many viewers. Further, it can be inconvenient for a number of different users to be required to constantly adjust the height of a chair. A chair designed to be at a vertical height to be comfortable for an average user (e.g., an individual having a height in a range determined to be an average adult height) could eliminate the need for many height adjustments; however, such a chair would fail to offer the benefit of adjustability necessary for users of non-average height.
The simplest solution to the plurality of heights among vertically adjustable chairs is to have the chair return to a predetermined height when the user removes his or her weight from the chair. That solution, however, creates its own disadvantages. If a chair user gets up momentarily (for example, to greet someone entering the room, or to retrieve an item from the other side of the room), the chair would return to its predetermined height, notwithstanding the user's intent to return to the chair shortly. Consequently, the user would be required to readjust the chair each time the user returns to the chair, even if having only risen momentarily.
Such an immediate return to a predetermined height can present further undesirable effects as well. For example, if the chairs were to return to their predetermined height as soon as the user gets up, on occasion, if many chair users in a single room were to arise, all of the chairs in a room may readjust their heights at the same time. This simultaneous readjustment could be a substantial distraction. Still further, immediate readjustment of the chair height could be a safety problem. For instance, if a user merely readjusted his or her weight, such as only partially arising to reach for an object, the chair height could readjust inopportunely, causing the user to fall.
In light of the above, it is desired to have a vertically adjustable chair that re-adjusts to its predetermined height sometime after the user leaves the chair. The present invention achieves this goal.